Persistent air leaks after lung surgery such as thoracentesis, lung biopsy or intercostal analgesic rib blocks are serious complications that result in increased morbidity and mortality as well as dramatically increased length of hospital stay. Air leaks can also occur spontaneously in a number of diseases. Most spontaneous air leaks result from rupture of blebs located at the apex of the lung. Air leaks following pulmonary procedures usually are due to incomplete apposition of the pulmonary parenchyma following resection. Fifteen percent of all patients undergoing pulmonary procedures develop air leaks and some studies have shown a prevalence as high as fifty-eight percent following lobectomy. Persistent air leaks, which are those that fail to resolve within one week, are the most frequent complication in patients undergoing general thoracic procedures.
A prolonged air leak can result in a broncho-pleural fistula—a nonhealing, abnormal communication between the lung and the chest cavity. Such fistulae may require drastic measures such as a thoracotomy with removal or repair of the affected lung and, possibly, placement of muscle or omental flaps into the chest cavity.
The patients who are predisposed to these problems, either spontaneously or iatrogenically, frequently have underlying medical problems (especially pulmonary) that make aggressive intervention a hazardous proposition. Prolonged air leaks can even result in patient death. Air leaks are the most frequent cause of extended hospital stay after thoracic surgery and results in significantly increased patient morbidity and hospital costs.
Detecting the location of an air leak is in and of itself a difficult problem. Current methods of diagnosis include high resolution cat scans, MRI's, and bronchoscopy for direct visualization of proximal airway leaks and bronchopleural fistulas. These modalities offer varying levels of reliability and satisfaction but are not consistently sensitive and accurate. The most definitive means to identify an air leak is through the relatively crude technique of open thoracotomy, in which the chest cavity is opened and filled with saline solution and then, following positive pressure ventilation, the location of bubble formation points to the area of leakage.
The current approach to repair of air leaks, once located, is to place a chest tube, if not already present, in the chest cavity with the leaking lung. If air is leaking from the lung after pulmonary surgery, chest tubes that are in place at the time of surgery can be used for this purpose. A conservative trial of applying suction to the intrathoracic tube to keep the lung expanded is the first maneuver. Occasionally, patients are discharged from the hospital with a one way “Heimlich” valve attached to the tube. This valve allows air leaking from the lung to escape from the chest cavity but does not allow air to enter and subsequently collapse the lung.
If these conservative measures do not work, a number of approaches have been attempted. Plugging the airway from within has been attempted by using a bronchoscope to attempt to localize the part of the lung that is healing and putting something into the lung to block airflow. The most common substance is fibrin glue. This technique has the shortcoming that the leak is not easy to localize if the leak is not from a readily visualized surgical bronchial stump. Thus, instilling a bronchial occluding agent into the airway will block off airflow to a significant portion of lung tissue that may or may not be the part that is leaking. In addition, this can cause pneumonia and respiratory failure.
Other techniques to seal air leaks involve approaching the leak from outside the lung. This, obviously, requires a major chest operation to mobilize and visualize the leak. The procedure is similar to finding a leak in a tire. The chest cavity is filled with saline, the lung is inflated and a search is initiated to localize the source of bubbles. Unlike a tire, however, the lung is a complexly shaped organ and it is frequently difficult, even with a major operation, to localize all leak sites. Once localized, the leaking area can be oversewn, stapled, resected or buttressed, as previously mentioned, with muscle flaps or omentum.
Recently, products have been introduced that act as sealants on the surface of the lung. These products are primarily used at the time of a pulmonary resection. The aim is to decrease the length of time that air leaks from areas of dissection or staple lines. Again, fibrin glue or other bioabsorbable sealants are applied and set on the lung surface intraoperatively. These products can only be applied to the outside of the lung in the setting of a major operation where the patient is under general anesthesia with selective lung ventilation.
Thus, a need exists for a minimally invasive system and method to detect and repair pulmonary air leaks.